* </p>
 *
 * <pre>
 * {@code
 * FtpClient ftpClient = new FtpClient();
 * ftpClient.init(); // Initialize with configured parameters
 * ResponseData responseData = ftpClient.doGet("ftp://example.com/path/to/file.txt");
 * // Process the responseData
 * ftpClient.close(); // Close and release resources
 * }
 * </pre>
 *
 * @author shinsuke
 */
public class FtpClient extends AbstractCrawlerClient {

- **CrawlerThread**: Individual crawler thread implementation

#### Client Architecture
- **HcHttpClient**: HTTP/HTTPS client using Apache HttpComponents
- **FileSystemClient**: File system access
- **FtpClient**: FTP protocol support
- **SmbClient**: SMB/CIFS network shares
- **StorageClient**: Cloud storage integration

#### Content Processing Pipeline
- **Extractors**: Content extraction from various formats

            final String owner = (String) responseData.getMetaDataMap().get(FtpClient.FTP_FILE_USER);
            if (owner != null) {
                roleTypeList.add(systemHelper.getSearchRoleByUser(owner));
            }
            final String group = (String) responseData.getMetaDataMap().get(FtpClient.FTP_FILE_GROUP);
            if (group != null) {

import org.codelibs.fess.Constants;
import org.codelibs.fess.crawler.client.CrawlerClientFactory;
import org.codelibs.fess.crawler.client.ftp.FtpAuthentication;
import org.codelibs.fess.crawler.client.ftp.FtpClient;
import org.codelibs.fess.crawler.client.http.HcHttpClient;
import org.codelibs.fess.crawler.client.http.config.CredentialsConfig;
import org.codelibs.fess.crawler.client.http.config.CredentialsConfig.CredentialsType;